The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Historically, cruise control systems incorporate a single closed loop control, which includes an integrator. An upper bound is applied to the closed loop control to avoid integrator wind-up. The upper bound is typically based on the throttle being fully open (WOT). To achieve necessary downshifts, a torque request must be able to increase above a maximum torque threshold in the current gear. Above the maximum torque threshold, a gasoline engine becomes unthrottled. When the cruise control increases the torque request above the maximum torque threshold using the closed loop control (integrator), but has not yet achieved a downshift, there is no additional response from the powertrain. The point of no additional response is integrator windup. Once the request increases sufficiently and the downshift occurs, the vehicle will begin to respond. However, the additional integrator windup can not be compensated for until the desired vehicle speed is achieved. Consequently, the vehicle speed increases beyond the set speed until the integrator windup has been compensated for.